It is proposed to continue with on-going attempts to demonstrate the biosynthesis of cholest-5-ene-3-beta, 26-diol in human aortal tissues, with 1,2-3H-cholesterol as precursor. Definitive proof of such biosynthesis is sought. We also seek to determine whether the mammalian brain sterol cholest-5-ene-3 beta 24-diol is also accumulated in the human aorta as is cholest-5-ene-3 beta 26-diol. We also will continue with our attempts to establish definitively whether cholest-5-ene-3 beta, 26-diol is present in human plasma, and whether its levels may be assayed suitably in reasonable-sized samples of human blood.